Two-component polyurethane pouring sealant and preparation method thereof

Abstract

The invention belongs to the technical field of high polymer materials, and discloses a two-component polyurethane pouring sealant and a preparation method thereof.The two-component polyurethane pouring sealant comprises a component A and a component B. The component A comprises, by weight, 40-60 parts of bio-based polyether polyol, 10-15 parts of boron nitride nanosheets, 5-10 parts of graphene modified epoxy resin, 1-3 parts of a silane coupling agent and 0.5-1.5 parts of a supercritical fluid foaming agent; the component B is prepared from 30 to 50 parts of carbodiimide modified MDI (methylene diphenyl diisocyanate), 10 to 20 parts of dendritic polyurethane cross-linking agent and 2 to 5 parts of nano aluminum hydroxide filler; the mixing ratio of the component A to the component B is (2-3): 1; the invention aims to provide the two-component polyurethane pouring sealant and the preparation method thereof, and through material innovation and process integration, the two-component polyurethane pouring sealant which is high in heat conductivity, environment-friendly, weather-resistant and low in internal stress is provided.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, in particular to a two-component polyurethane potting adhesive and a preparation method thereof. Background Art

[0002] Two-component polyurethane encapsulant is a key material in electronic packaging, new energy equipment, and other fields. Its performance directly impacts the reliability and safety of end products. However, with technological advancements in high-end fields such as 5G communications, new energy vehicles, and aerospace, existing technologies are facing significant bottlenecks in multiple areas, making it difficult to meet stringent application requirements.

[0003] In terms of electrical performance, traditional potting compounds commonly use fillers such as graphene to improve thermal conductivity. However, such fillers can easily damage the insulation structure, resulting in a volume resistivity below 10¹³Ω・cm, posing a leakage risk in the 800V high-voltage battery system of new energy vehicles. Their dielectric constant (1kHz) is often 4.0-4.5, and the dielectric loss tangent is greater than 0.02, which cannot meet the low signal attenuation requirements of 5G high-frequency devices (frequency bands above 28GHz), thus restricting the stability of communication equipment.

[0004] In terms of service performance in complex environments, existing products are prone to brittle cracking below -40°C, and their strength decays by more than 30% after long-term service above 120°C. In addition, the homogeneous structure makes it difficult to balance impact resistance and support stiffness, leading to cracking of chip packaging or displacement of battery modules. The agglomeration of micron-level fillers causes the water absorption rate to exceed 1.0%, and interfacial debonding and electromigration failure are prone to occur in high humidity or marine environments. The volume expansion rate is greater than 15% when immersed in electrolyte, and the sealing function is lost.

[0005] In terms of environmental protection and sustainability, traditional formulas rely on petroleum-based polyether (bio-based content <20%), with a production carbon emission intensity of 5.2kgCO2 / kg, and contain harmful substances such as phthalates, which do not meet REACHSVHC control requirements; the chemical foaming process VOC emissions are >50g / L, and after disposal, it is difficult to degrade and recycle due to the cross-linked structure, resulting in waste of resources and environmental pollution.

[0006] In summary, the existing technology has multiple technical gaps in high thermal conductivity-insulation balance, wide temperature range reliability, green manufacturing and adaptability to complex scenarios. Therefore, in order to solve the above problems, a two-component polyurethane potting adhesive and a preparation method thereof are proposed to solve the above problems. Summary of the Invention

[0007] The present invention aims to provide a two-component polyurethane potting adhesive and a preparation method thereof, and through material innovation and process integration, provide a two-component polyurethane potting adhesive with high thermal conductivity, environmental protection, weather resistance and low internal stress.

[0008] In order to achieve the above object, the present invention provides the following technical solutions: The technical solution provided by the present invention is: a two-component polyurethane potting adhesive, which includes component A and component B, calculated by weight: Component A includes: 40-60 parts of bio-based polyether polyol, 10-15 parts of boron nitride nanosheets, 5-10 parts of graphene-modified epoxy resin, 1-3 parts of silane coupling agent, and 0.5-1.5 parts of supercritical fluid foaming agent; Component B includes: 30-50 parts of isocyanate prepolymer, 10-20 parts of dendritic polyurethane crosslinker, and 2-5 parts of nano-aluminum hydroxide filler; The isocyanate prepolymer is derived from alicyclic isocyanate HDI or aromatic isocyanate MDI; The mixing ratio of component A to component B is (2-3):1.

[0009] Furthermore, the bio-based polyether polyol is a castor oil-based polyether polyol or a soybean oil-based polyether polyol, has a hydroxyl value of 30-60 mgKOH / g, and a bio-based content of ≥80%; The boron nitride nanosheets are modified by melamine-cyanuric acid or dopamine-silane, have an average particle size of 50-100 nm, and are grafted with amino groups or dopamine groups on the surface.

[0010] Furthermore, the mass fraction of graphene in the graphene-modified epoxy resin is 2-4%, and it is prepared by in-situ polymerization to form a three-dimensional thermal conductive network; The dendritic polyurethane crosslinker is a dendritic polymer with multiple hydrogen bond and coordination bond active sites, which forms a three-dimensional crosslinked network through a branched structure.

[0011] Furthermore, the supercritical fluid foaming agent is supercritical carbon dioxide, which is introduced during the preparation of component A to form a closed-cell structure with a pore size of 50-200 μm.

[0012] Furthermore, a method for preparing a two-component polyurethane potting adhesive comprises the following steps: S1: Preparation of component A: mixing bio-based polyether polyol with supercritical carbon dioxide in a high-pressure reactor and subjecting it to supercritical fluid foaming treatment at 10-15 MPa and 35-45°C for 2-3 hours; Add boron nitride nanosheets, graphene-modified epoxy resin, and silane coupling agent, and disperse at a speed of 1500-2000 rpm for 40-60 minutes to form a uniform thermal conductive-foaming composite system; S2: Preparation of component B: reacting carbodiimide-modified MDI with a dendritic polyurethane crosslinker at 60-70°C for 2-3 hours to form a prepolymer; Add nano-aluminum hydroxide filler and stir for 10-15 minutes to prepare component B; S3: Mixing: Mix component A and component B in proportion and cure at room temperature for 12-24 hours to form a potting compound with a gradient foaming structure.

[0013] Furthermore, the pressure of the supercritical fluid foaming treatment in S1 is 12 MPa, the temperature is 40° C., and the amount of the foaming agent added is 1-2% by weight of the bio-based polyether polyol.

[0014] Furthermore, the amount of the dendritic polyurethane crosslinker added in S2 is 10-15% by weight of the carbodiimide-modified MDI.

[0015] The beneficial effects of this technical solution are: (1) The introduction of boron nitride nanosheets (BNNS) not only builds an efficient thermal conduction path but also maintains excellent insulation performance (volume resistivity ≥ 10¹ 4 Ω・cm, 50% higher than traditional graphene-based potting compounds), avoiding the risk of leakage and suitable for high-voltage electronic devices; The dense cross-linked network formed by the dendritic cross-linker can inhibit ion migration, and the leakage current is less than 1μA at a DC voltage of 1000V, meeting the IEC60243-1 insulation test standard; Low dielectric loss: The combination of bio-based polyether polyol and isocyanate prepolymer reduces the dielectric constant (1kHz) of the potting compound to 3.2-3.5, and the dielectric loss tangent is less than 0.01, which is significantly lower than traditional aromatic polyurethane (dielectric constant 4.0-4.5, loss tangent 0.02-0.03) and isocyanate prepolymer (which can be selected from alicyclic isocyanates such as HDI and aromatic isocyanates such as MDI).

[0016] (2) After 100 cycles of temperature from -40°C to 120°C, the tensile strength retention rate is >90%, which is significantly improved compared to the 70-80% retention rate of the existing technology; The closed-cell structure (closed-cell ratio > 90%) formed by supercritical foaming effectively blocks water vapor penetration, with a water absorption rate of < 0.3% (ASTM D570 standard), extending the service life in high humidity environments; The gradient foaming structure (inner layer pore size 150-200μm, outer layer 80-100μm) enables the potting compound to provide both rigid support (surface hardness Shore A75-85) and flexible cushioning (compression rebound rate >85%). In a 1m drop impact test, the peak stress of the protected device is reduced by 40%, effectively resolving the contradiction between traditional potting compounds' "hard and brittle cracking" and "insufficient soft support."

[0017] (3) Raw material side: The replacement rate of bio-based polyether polyols (castor oil / soybean oil-based) is ≥80%, reducing dependence on petroleum resources. The carbon emission intensity of the production process is reduced by 45% compared with traditional processes (calculated according to ISO14064); Process: Supercritical carbon dioxide foaming technology uses no solvent, with VOC emissions less than 10g / L (GB30981-2020 standard limit of 50g / L), and carbon dioxide can be recycled (recovery rate > 95%), avoiding the toxicity of decomposition products of traditional chemical foaming agents (such as azodicarbonamide); Waste end: The potting compound can be recycled into polyol and isocyanate monomers through alkaline hydrolysis, with a recovery rate of >80%, which meets the requirements of circular economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a data table of Example 1 of a two-component polyurethane potting adhesive and a preparation method thereof proposed in the present invention; Figure 2 This is a data table of Example 2 of a two-component polyurethane potting adhesive and a preparation method thereof proposed in the present invention; Figure 3 This is a data table of Example 3 of a two-component polyurethane potting adhesive and a preparation method thereof proposed in the present invention; Figure 4 This is a data table of Example 4 of a two-component polyurethane potting adhesive and a preparation method thereof proposed in the present invention; Figure 5 This is a data table of Example 5 of a two-component polyurethane potting adhesive and a preparation method thereof proposed in the present invention; Figure 6 This is a data table of Example 6 of a two-component polyurethane potting adhesive and a preparation method thereof proposed in the present invention; Figure 7 This is a table showing the beneficial effects of a two-component polyurethane potting adhesive and a preparation method thereof proposed in the present invention; Figure 8 This is a data comparison table of Examples 1-6 of a two-component polyurethane potting adhesive and a preparation method thereof proposed in the present invention; Figure 9 This is a data comparison table of the present invention and the prior art for a two-component polyurethane potting adhesive and a preparation method thereof proposed by the present invention. DETAILED DESCRIPTION

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0020] The specific implementation process is as follows: Example 1: See also Figure 1 The present invention provides a technical solution: a method for preparing a two-component polyurethane potting adhesive, comprising the following steps: S1: Preparation of component A: 50 parts of castor oil-based polyether polyol (hydroxyl value 45 mgKOH / g, bio-based content 85%) were added to the autoclave.

[0021] Supercritical carbon dioxide (pressure 12 MPa, temperature 40°C) was injected and stirred for 2 hours to form a uniform sol.

[0022] 12 parts of melamine-cyanuric acid modified BNNS (average particle size 80 nm, surface grafted amino groups), 8 parts of graphene-modified epoxy resin (graphene content 3%), and 2 parts of γ-aminopropyltriethoxysilane were added and dispersed at 1800 rpm for 50 minutes.

[0023] Vacuum degassing for 15 minutes to obtain component A.

[0024] S2: Preparation of component B: 40 parts of carbodiimide-modified MDI (NCO content 10%) and 15 parts of a dendritic polyurethane crosslinker, which is an ethylenediamine-G2-urea-pyridine dendritic polyurethane crosslinker (crosslink density 60%), are reacted at 65°C for 2.5 hours.

[0025] 3 parts of nano-aluminum hydroxide filler (particle size 50 nm) were added and stirred for 12 minutes to prepare component B.

[0026] S3: Mixing and curing: Mix according to A:B=2.5:1, and cure at room temperature for 18 hours to form a gradient foaming structure (inner layer pore size 150μm, outer layer pore size 80μm).

[0027] Performance Testing Thermal conductivity: 3.8W / m・K Tensile strength: 16.5MPa Flame retardant grade: UL94V-0 Yellowing index ΔE: 2.1 (after 1000 hours of UV aging).

[0028] Example 2: See also Figure 2 The present invention provides a technical solution: a method for preparing a two-component polyurethane potting adhesive, comprising the following steps: S1: Preparation of component A: 50 parts of soybean oil-based polyether polyol (hydroxyl value 55 mgKOH / g, bio-based content 82%) were added to the autoclave.

[0029] Supercritical carbon dioxide (pressure 12 MPa, temperature 40°C) was injected and stirred for 2 hours to form a uniform sol.

[0030] Add 12 parts of dopamine-silane modified BNNS (average particle size 80 nm, dopamine groups grafted on the surface), 8 parts of graphene modified epoxy resin (graphene content 3%), and 2 parts of γ-aminopropyltriethoxysilane, and disperse at 1800 rpm for 50 minutes.

[0031] Vacuum degassing for 15 minutes to obtain component A.

[0032] S2: Preparation of component B: 40 parts of carbodiimide-modified MDI (NCO content 10%) and 15 parts of a dendritic polyurethane crosslinker, which is an ethylenediamine-G2-urea-pyridine dendritic polyurethane crosslinker (crosslink density 60%), are reacted at 65°C for 2.5 hours.

[0033] 3 parts of nano-aluminum hydroxide filler (particle size 50 nm) were added and stirred for 12 minutes to prepare component B.

[0034] S3: Mixing and curing: Mix according to A:B=2.5:1, and cure at room temperature for 18 hours to form a gradient foaming structure (inner layer pore size 150μm, outer layer pore size 80μm).

[0035] Performance Testing Thermal conductivity: 3.6W / m・K Tensile strength: 17.2MPa Flame retardant grade: UL94V-0 Yellowing index ΔE: 1.8.

[0036] Embodiment three: See also Figure 3 The present invention provides a technical solution: a method for preparing a two-component polyurethane potting adhesive, comprising the following steps: S1: Preparation of component A: 50 parts of castor oil-based polyether polyol (hydroxyl value 45 mgKOH / g, bio-based content 85%) were added to the autoclave.

[0037] Supercritical carbon dioxide (pressure 10 MPa, temperature 35°C) was injected and stirred for 2 hours to form a uniform sol.

[0038] 12 parts of melamine-cyanuric acid modified BNNS (average particle size 80 nm, surface grafted amino groups), 10 parts of graphene-modified epoxy resin (graphene content 3%), and 2 parts of γ-aminopropyltriethoxysilane were added and dispersed at 1800 rpm for 50 minutes.

[0039] Vacuum degassing for 15 minutes to obtain component A.

[0040] S2: Preparation of component B: 40 parts of alicyclic isocyanate HDI (NCO content 12%) and 15 parts of a dendritic polyurethane crosslinker, wherein the dendritic polyurethane crosslinker is an ethylenediamine-G2-urea-pyridine dendritic polyurethane crosslinker (crosslink density 60%), and react at 65°C for 2.5 hours.

[0041] 3 parts of nano-aluminum hydroxide filler (particle size 50 nm) were added and stirred for 12 minutes to prepare component B.

[0042] S3: Mixing and curing: Mix according to A:B=2.5:1, and cure at room temperature for 18 hours to form a gradient foaming structure (inner layer pore size 200μm, outer layer pore size 100μm).

[0043] Performance Testing Thermal conductivity: 4.0W / m・K Tensile strength: 15.8MPa Flame retardant grade: UL94V-0 Yellowing index ΔE: 1.5.

[0044] Example 4: See also Figure 4 , a comparative technical solution provided by the present invention: a preparation method of a two-component polyurethane potting adhesive, comparative example 1: The following steps are involved: S1: Preparation of component A: 50 parts of petroleum-based polyether PPG-2000 (hydroxyl value 56 mgKOH / g) were added to the reactor.

[0045] 20 parts of micron-sized aluminum oxide (particle size 5 μm), 8 parts of ordinary epoxy resin, and 2 parts of γ-aminopropyltriethoxysilane were added and dispersed at 1800 rpm for 50 minutes.

[0046] Vacuum degassing for 15 minutes to obtain component A.

[0047] S2: Preparation of component B: 40 parts of traditional MDI (NCO content 15%) and 15 parts of a common crosslinker (trimethylolpropane) were reacted at 65°C for 2.5 hours.

[0048] 3 parts of nano-aluminum hydroxide filler (particle size 50 nm) were added and stirred for 12 minutes to prepare component B.

[0049] S3: Mixing and curing: Mix according to A:B=2.5:1, and cure at room temperature for 18 hours to form a uniform foaming structure (pore size 500μm).

[0050] Performance Testing Thermal conductivity: 1.2W / m・K Tensile strength: 8.5MPa Flame retardant grade: UL94V-1 Yellowing index ΔE: 6.3.

[0051] Embodiment 5: See also Figure 5 , a technical solution provided by the present invention: a preparation method of a two-component polyurethane potting adhesive, comparative example 2: The following steps are involved: S1: Preparation of component A: 50 parts of castor oil-based polyether polyol (hydroxyl value 45 mgKOH / g, bio-based content 85%) were added to the autoclave.

[0052] Supercritical carbon dioxide (pressure 12 MPa, temperature 40°C) was injected and stirred for 2 hours to form a uniform sol.

[0053] 12 parts of unmodified BNNS (average particle size 80 nm), 8 parts of graphene-modified epoxy resin (graphene content 3%), and 2 parts of γ-aminopropyltriethoxysilane were added and dispersed at 1800 rpm for 50 minutes.

[0054] Vacuum degassing for 15 minutes to obtain component A.

[0055] S2: Preparation of component B: 40 parts of carbodiimide-modified MDI (NCO content 10%) and 15 parts of a common crosslinking agent (trimethylolpropane) were reacted at 65°C for 2.5 hours.

[0056] 3 parts of nano-aluminum hydroxide filler (particle size 50 nm) were added and stirred for 12 minutes to prepare component B.

[0057] S3: Mixing and curing: Mix according to A:B=2.5:1, and cure at room temperature for 18 hours to form a gradient foaming structure (inner layer pore size 150μm, outer layer pore size 80μm).

[0058] Thermal conductivity: 2.5W / m・K Tensile strength: 11.2MPa Flame retardant grade: UL94V-0 Yellowing index ΔE: 3.2.

[0059] Example 6: See also Figure 6 , a technical solution provided by the present invention: a preparation method of a two-component polyurethane potting adhesive, comparative example 3: The following steps are involved: S1: Preparation of component A: 50 parts of castor oil-based polyether polyol (hydroxyl value 45 mgKOH / g, bio-based content 85%) were added to the autoclave.

[0060] Supercritical carbon dioxide (pressure 12 MPa, temperature 40°C) was injected and stirred for 2 hours to form a uniform sol.

[0061] 12 parts of melamine-cyanuric acid modified BNNS (average particle size 80 nm, surface grafted amino groups), 8 parts of graphene-modified epoxy resin (graphene content 3%), and 2 parts of γ-aminopropyltriethoxysilane were added and dispersed at 1800 rpm for 50 minutes.

[0062] Vacuum degassing for 15 minutes to obtain component A.

[0063] S2: Preparation of component B: 40 parts of traditional MDI (NCO content 15%) and 15 parts of a common crosslinker (trimethylolpropane) were reacted at 65°C for 2.5 hours.

[0064] 3 parts of nano-aluminum hydroxide filler (particle size 50 nm) were added and stirred for 12 minutes to prepare component B.

[0065] S3: Mixing and curing: Mix according to A:B=2.5:1, and cure at room temperature for 18 hours to form a gradient foaming structure (inner layer pore size 150μm, outer layer pore size 80μm).

[0066] Performance Testing Thermal conductivity: 3.1W / m・K Tensile strength: 13.5MPa Flame retardant grade: UL94V-0 Yellowing index ΔE: 4.8.

[0067] See also Figure 8 Comparison table of various embodiments, 1. Boron nitride nanosheet (BNNS) modification: Example 1 (modified BNNS) achieved a thermal conductivity of 3.8 W / m·K, significantly higher than that of Comparative Example 5 (unmodified BNNS, 2.5 W / m·K). This demonstrates that surface grafting (melamine-cyanuric acid / dopamine) can improve the dispersibility of BNNS in bio-based polyether (reducing aggregate size from 500 nm to below 150 nm), thereby creating a highly efficient thermal conductivity pathway (increasing thermal conductivity by 52%). Furthermore, the modified BNNS maintains a volume resistivity of 1.2 × 10¹ 4 Ω・cm (Comparative Example 5 is 8×10¹³Ω・cm), achieving a high thermal conductivity-insulation balance.

[0068] Effect of the dendritic crosslinker: The tensile strength of Example 1 (G2 generation crosslinker) is 16.5 MPa, significantly higher than that of Comparative Example 6 (traditional crosslinker, 13.5 MPa), proving that the three-dimensional branched structure can increase the crosslinking density by 40-60% and effectively disperse stress. The dielectric loss tangent (0.012) is lower than that of Comparative Example 6 (0.018), indicating that the multiple hydrogen bonds of the dendritic molecules reduce the dipole polarization loss, meeting the high-frequency and low-loss requirements of 5G.

[0069] Advantages of isocyanate: The yellowing index of Example 3 (HDI) is ΔE=1.5 (1000h UV aging), which is much better than that of Comparative Example 6 (traditional MDI, ΔE=4.8).

[0070] 2. Functional balance of the gradient foaming structure: Examples 1-3 all use supercritical carbon dioxide foaming (closed cell rate > 90%) and a pore size gradient distribution (inner layer 150-200μm buffer, outer layer 80-100μm support), so that the compression rebound rate reaches 83-87% (compared to only 70% for homogeneous foaming in Example 4) and the water absorption rate is less than 0.3% (compared to 1.2% in Example 4). This solves the contradiction between "hard and brittle cracking" and "insufficient soft support" of traditional potting glue, and is suitable for battery module impact resistance and chip packaging low-stress scenarios.

[0071] See also Figure 7 and Figure 9 , the beneficial effects of the present invention and the comparison table of each embodiment with the prior art 1. Excellent thermal conductivity and insulation: The thermal conductivity of the existing technology is 1.8W / m・K, while the present invention reaches 3.8W / m・K (an increase of 111%), and the volume resistivity is 1-2 orders of magnitude higher (1.2×10¹ 4 Ω・cmvs5×10¹²Ω・cm), solving the heat dissipation and leakage risks of high-voltage electronic devices (such as 800V battery systems).

[0072] Reliability over a wide temperature range: The existing technology has a strength attenuation of >30% after long-term service at 120°C. The present invention, through the synergy of bio-based polyether and dendritic crosslinker, has a strength retention rate of >90% after cycling from -40°C to 120°C, and a tensile strength of 15-17MPa (<10MPa in the existing technology), meeting the extreme environmental requirements of aerospace equipment.

[0073] High-frequency signal adaptability: The dielectric constant of the present invention is 3.2-3.5 and the loss tangent is 0.010-0.012, which are superior to the existing technology (dielectric constant 4.0-4.5, loss tangent 0.022-0.025). The signal attenuation in the 28GHz frequency band is less than 1dB (the existing technology is greater than 3dB), ensuring the signal integrity of 5G communication equipment.

[0074] 2. Bio-based raw material substitution: The bio-based content of this invention is ≥80% (existing technology <20%), and the carbon footprint is reduced by 45%, meeting the green manufacturing standards.

[0075] Clean production process: Supercritical foaming has no solvent residue (VOC < 10g / L), reducing emissions by 80% compared to existing chemical foaming (VOC > 50g / L); waste glue can be alkaline-hydrolyzed to recover monomers (recovery rate > 80%), solving the environmental problem of "single-use" of traditional cross-linked polyurethane.

[0076] 3. Room temperature curing and efficient production: The room temperature curing time of this invention is 12-18 hours, without the need for oven heating (the existing technology requires 80°C × 4 hours), and the energy consumption of a single batch is reduced by 30%. The pot life is extended to 4 hours (the existing technology is less than 1 hour), which facilitates on-site potting of large equipment and improves production efficiency by 50%.

[0077] Optimized filler efficiency: The target thermal conductivity can be achieved with only 10-15 parts of nano-scale BNNS added (existing technology requires more than 30 parts of micron filler). The system viscosity is less than 8000 mPa·s (existing technology >10000 mPa·s), the dispersion process is simplified, and the filler cost is reduced by 20%.

[0078] The core benefits of this technology compared to existing technologies 1. Thermal conductivity increased by 200%: Through the composite of BNNS and graphene nanometers, a three-dimensional thermal conductive path is constructed, breaking through the thermal conductivity bottleneck of traditional micron fillers and meeting the heat dissipation needs of high-power devices (such as 5G base stations and battery packs).

[0079] Weather resistance improved by 60%: Alicyclic isocyanate and gradient curing process reduce the yellowing index to 1.5-2.1 (existing technology >5), performance retention rate after 1000 hours of UV aging >90%, and service life extended by more than 100%.

[0080] Mechanical-insulating balance: dendritic crosslinkers enable tensile strengths of 15-17 MPa (existing technology <10 MPa), while volume resistivity ≥10¹ 4 Ω・cm, solving the technical contradiction of "high strength-high insulation".

[0081] 2. Bio-based substitution rate ≥ 80%: Reduce dependence on petroleum resources.

[0082] Zero VOC and recyclable: Supercritical foaming technology eliminates solvent pollution from the source, and the recycling rate of waste rubber is >80%, filling the gap of existing technology in the field of circular economy.

[0083] Through nano-scale filler modification, bio-based material substitution, dendritic cross-linker design, and supercritical foaming process, this technology comprehensively surpasses existing technologies in key indicators such as thermal conductivity, weather resistance, environmental protection, and process adaptability. It not only solves the performance shortcomings of traditional potting glue, but also opens up high-end application scenarios such as high pressure, high frequency, and wide temperature range.

[0084] The above is only an embodiment of the present invention, and common knowledge such as the specific technical solutions or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the description can be used to interpret the content of the claims.

Claims

1. A two-component polyurethane potting adhesive, characterized by: Two-component polyurethane potting adhesive includes component A and component B, calculated by weight: Component A includes: 40-60 parts of bio-based polyether polyol, 10-15 parts of boron nitride nanosheets, 5-10 parts of graphene-modified epoxy resin, 1-3 parts of silane coupling agent, and 0.5-1.5 parts of supercritical fluid foaming agent; Component B includes: 30-50 parts of isocyanate prepolymer, 10-20 parts of dendritic polyurethane crosslinker, and 2-5 parts of nano-aluminum hydroxide filler; The isocyanate prepolymer is derived from alicyclic isocyanate HDI or aromatic isocyanate MDI; The mixing ratio of component A to component B is (2-3):

1.

2. The two-component polyurethane potting adhesive according to claim 1, characterized in that: The bio-based polyether polyol is castor oil-based polyether polyol or soybean oil-based polyether polyol, has a hydroxyl value of 30-60 mgKOH / g, and a bio-based content of ≥80%; The boron nitride nanosheets are modified by melamine-cyanuric acid or dopamine-silane, have an average particle size of 50-100 nm, and are grafted with amino groups or dopamine groups on the surface.

3. The two-component polyurethane potting adhesive according to claim 1, characterized in that: The mass fraction of graphene in the graphene-modified epoxy resin is 2-4%, and it is prepared by in-situ polymerization to form a three-dimensional thermal conductive network; The dendritic polyurethane crosslinking agent is a dendritic polymer having multiple hydrogen bonds and coordination bond active sites, and forms a three-dimensional crosslinking network through a branched structure.

4. The two-component polyurethane potting adhesive according to claim 1, characterized in that: The supercritical fluid foaming agent is supercritical carbon dioxide, which is introduced during the preparation of component A to form a closed-cell structure with a pore size of 50-200 μm.

5. A method for preparing a two-component polyurethane potting adhesive according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1: Preparation of component A: mixing bio-based polyether polyol with supercritical carbon dioxide in a high-pressure reactor and subjecting it to supercritical fluid foaming treatment at 10-15 MPa and 35-45°C for 2-3 hours; Add boron nitride nanosheets, graphene-modified epoxy resin, and silane coupling agent, and disperse at a speed of 1500-2000 rpm for 40-60 minutes to form a uniform thermal conductive-foaming composite system; S2: Preparation of component B: reacting carbodiimide-modified MDI with a dendritic polyurethane crosslinker at 60-70°C for 2-3 hours to form a prepolymer; Add nano-aluminum hydroxide filler and stir for 10-15 minutes to prepare component B; S3: Mixing: Mix component A and component B in proportion and cure at room temperature for 12-24 hours to form a potting compound with a gradient foaming structure.

6. The method for preparing the two-component polyurethane potting adhesive according to claim 5, characterized in that: The pressure of the supercritical fluid foaming treatment in S1 is 12 MPa, the temperature is 40° C., and the amount of foaming agent added is 1-2% by weight of the bio-based polyether polyol.

7. The method for preparing the two-component polyurethane potting adhesive according to claim 5, characterized in that: The amount of the dendritic polyurethane crosslinker added in S2 is 10-15% of the weight of the carbodiimide-modified MDI.

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